Pump for molten metal and the like



e 1934- J. E. RHOADS ET AL 1,947,876

PUMP FOR MOLTEN METAL AND THE LIKE Filed July 10. 1951 lwvervorfi J Zd 0:7" 255750624655 (72 555675 Wie Patented eb.,-

;,a riitat w Joseph Edgar Rhoads,

Wilmington, Del., and

George Herbert White, Philadelphia, Pa., assignors, by mesne assignments, to Chester A, Macomic, Chicago, Ill.

Application July 10, 1931. Serial No. 549,935

2 Claims.

Our invention relates to improvements in pumps for molten metal and the like, and has for one object to provide a pump especially adapted for use in connection with lead and other molten 5 metals, wherein the opposed piston and cylinder surfaces will be self -cleaning, and wherein a minimum of deposit of non-fluid refuse material may take place.

Experience shows that when lead or similar metals, and particularly when lead alloys used for casting bullets, type slugs and the like are pumped in connection with the casting process, there is a. formation of dry non-fluid granular or dust like material on the opposed working piston and cylinder surfaces. This deposit gradually builds up on the working surfaces and ultimately binds them against movement. The deposit is lighter than themolten metal, and if it can be floated in the metal it will be washed off the surgo faces and rise to the top. However, when the clearances between the plunger and cylinder are small enough to provide satisfactory pumping conditions, experience shows that not enough molten lead penetrates between these surfaces to wash that material away and the material gradually builds up, adheres to and jams between the piston and the cylinder surfaces.

This powder perhaps is lead oxide, perhaps it is a deposit formed by impurities in the lead but in any event It builds up or forms when a thin film of molten lead is heated for any length of time. This decomposition of the thin film of molten metal or this deposit of refuse out of a thin film of molten metal apparently takes place whether the surfaces in opposition are moving or not. It apparently takes place exposed to the air or not and our solution of the problems arising as a result of this decomposition of the lead film or this deposition of refuse from the lead film which binds the working surfaces together consists in so disposing the pump and the cylinder that substantially all of the surfaces of one or the other or both of the moving parts will pe- 0 moving surfaces.

\ One mechanical solution of the difllculty takes the form of a cylinder radially apertured, a piston reciprocating in the cylinder, the radial apertures being so arranged or so staggered that during its movement in the cylinder every part of the piston surface at one time or another is in register with one .of said apertures. Where this is impossible for instance at the lower end of the piston excursion where the cylinder must be closed to permit the piston to develop pressure against 00 the molten surface, the inner wall of the cylinder is relieved so as to avoid any actual contact between the piston and the cylinder wall.

In general, therefore, what we propose to do is to provide a piston cylinder combination 05 wherein there is a contacting surface between the piston and the cylinder wall to guide the piston and make a closure immediately adjacent the pressure zone, which wall will be so thin that all of the remaining piston cylinder contacting surfaces may be relieved either by perforations, slots or any other suitable arrangement to insure that substantially all of the piston surface is periodically bathed in the molten metal and that those parts of the mating piston cylinder surfaces that are not periodically or constantly bathed in molten metal will be frequently brought into opposition with parts on the opposed member which are so bathed in the molten metal whereby any deposit formed on either member so will by the relative movement of the two members be scraped or forced off into the bath and be free to rise to the surface. It will be understood that while we have shown in our preferred form a skeleton cylinder provided with radial 5 apertures, the same result might be formed by any other arrangement of piston and cylinder which would accomplish this desired result and it is not necessary that the perforations be limited to the cylinder or that they be the type of perforations shown or that they extend clear through the cylinder or piston. Under some circumstances the apertures might be dispensed with and the result obtained by merely providing greatly increased clearance between the major portion of the mating piston-cylinder surfaces.

Our invention is illustrated more or less d1- agrammatically in the accompanying drawing, wherein v Figure 1 is a detailed sectional view of a molten pot, pump and cylinder;

Figure 2 is a plan view of the cylinder;

Figure 3 is a detailed side elevation of the cylinder;

Figure 4 is a development of the cylinder bore.

Figures 5 and 6 illustrate a modified form of cylinder.

Like parts are indicated by like characters throughout the specification and drawing.

A is a pot adapted to contain molten metal. A are electric heating elements adapted to heat the metal in the pot. A is a conduit disposed in the wall of the pot leading to the casting nozzle A A is a cylinder socket in the wall of the pot communicating with the conduit.

B is the cylinder. It is flanged at B lower end of the cylinder has an extension B adapted to engage the socket and the upper portion of the cylinder B projects upwardly from the flange B being located in the body of the molten metal. This cylinder is countersunk at B to guide the piston when it isinserted in a bath of molten lead and the cylindrical portion of the cylinder is drilled or apertured as indicated especially in Figure 4, there being a series of staggered holes formed radially in the cylinder wall so that the holes and the inner periphery of the cylinder overlap, the result being that there is in efiect no dead area.

These holes are the holes 0 C C C 0* arranged in groups about the periphery of the cylinder and spaced above the flange B The series of holes C immediately above the flange B serve as intake ports and when the piston D is retracted it is drawn up so that its working face lies above the lower portions of the ports C and lead may flow in through these holes serving as intake ports ready for the next stroke.

Since the piston is not retracted above the holes C the intermediate end of the piston is associated with blank spots D D where no holes are located. To take care of this situation the cylinder is interiorly expanded ,in register with the holes C as at D so while the piston is not cleared there by holes, it is cleared by the clearance between the piston and the interior of the cylinder. The means for operating the pump are not shown and the details involving the distribution of the molten metal are not shown as they form no part of the present invention.

In the modified form shown in Figures 5 and following we illustrate a diiferent exemplification of our device where instead of providing a series of spaced holes in the wall of the cylinder, the cylinder takes the form of a cage E made up of a series of spiral ribs E whose area is much The less than the total geometric surface of the cylinder. These spiral ribs are so disposed that they guide the piston and plunger but further so disposed that as the piston E reciprocates every part of it where it is engaged by these ribs is periodically immersed in the bath out of register with the guiding ribs. In this case the plunger at its lower end is reduced as at E the cylinder is not. The same effect is produced imme iate- 1y above the intake point, the result being hat the cylinder is continuous only throughout the very small area which is substantially equivalent to the stroke of the piston and when the piston at its reduced end comes in contact with the part of the cylinder which is reduced in diameter below the intake port, refuse or deposit between those surfaces will be washed off in the same way because it is only at the time that casting takes place that the two mating surfaces are in juxtaposition.

We claim:

1. A pump for molten metal and the like comprising a cylinder and piston mounted for reciprocation therein, the cylinder wall being apertured, the apertures being arranged in groups about the periphery of the cylinder, the groups being disposed along the axis of the cylinder, the apertures in one group being angularly displaced with respect to the apertures in the next so that as the piston reciprocates all parts of the surface thereof during the cycle of operation come in register with at least one of said apertures.

2. A pump for molten metal and the like comprising a pumping piston mounted for reciprocation in a bath of molten metal, guide means for the piston comprising a cylindrical member in which the piston is guided, said guide means being so disposed with respect to the piston that as the piston reciprocates substantially all of the piston area is periodically out of contact with the guide means, the guide means comprising an apertured guide cylinder, the apertures being arranged along lines inclined to the path of reciprocation of the piston.

J. EDGAR RHOADS. G. HERBERT WHITE. 

